Fabrication and enhanced visible-light photocatalytic activity of Pt-deposited TiO2 hollow nanospheres

To use visible light more effectively in photocatalytic reactions, well-defined Pt-modified hollow TiO2 (HPT) spheres were prepared through a hydrothermal-synthesis process using carbon spheres as templates, followed by calcinations and photochemical reduction. The photocatalysts were characterized by a number of techniques, including X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and photoluminescence measurements. The photocatalytic activity of the fabricated HPT photocatalyst for the degradation of methylene blue under visible-light irradiation was determined. The HPT photocatalyst with a Pt/TiO2 mass ratio of 0.75% exhibits the optimal photocatalytic ability at a catalyst amount of 2 g L-1. The pseudo-first-order rate constant k(app) for 0.75% HPT is five times that for solid TiO2 nanoparticles (P25) and three times that for hollow TiO2. Hydroxyl and superoxide radical signals were detected by means of electron paramagnetic resonance spectroscopy; these radicals are most probably responsible for the effectiveness of the HPT photocatalyst. (C) 2013 Elsevier B.V. All rights reserved.